1. Field of the Invention
The present invention generally relates to an interlock mechanism and an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multifunction machine capable of at least two of these functions, that incorporates the interlock mechanism.
2. Description of the Background Art
Image forming apparatuses having an openably closable cover that opens and closes relative to an apparatus body generally include as a safety measure an interlock mechanism to deactivate the apparatus when the cover is opened, securing the safety of users. In particular, image forming apparatuses typically include multiple covers because the direction in which sheets of recording media are transported and the direction in which consumables are inserted into the apparatus are different. These covers are opened during replacement of consumables or removal of jammed sheets. When any one cover is opened, however, it is difficult to physically block access to all hazardous components, such as motors, high-pressure components, and laser beam paths, inside the apparatus. Therefore, interlock mechanisms that operate in conjunction with opening and closing of the cover are used. Although a micro switch may be provided for each cover when the apparatus includes multiple covers to deactivate the apparatus when any cover is opened, using multiple micro switches is not desirable.
In view of the foregoing, several approaches described below have been tried. For example, JP-3754777-B proposes a single lever that moves when pushed in two different directions. When a first cover and a second cover are closed, the lever is moved to a position to push the micro switch of the interlock mechanism, turning it on. This approach, however, has several drawbacks. For example, because the operational range of an actuator to turn on and of the micro switch is as small as several millimeters, in such a configuration, over strokes of the cover that is closed or variations in the size of components cannot be absorbed, resulting in deformation of or damage to the micro switch.
To overcome this problem, JP-2008-037054-A proposes an actuator that moves in a direction different from a direction in which the cover moves when the cover is fully closed so that no abrupt force is applied to the micro switch when the cover is closed. Still, as described above severe limitations in the operational range of the actuator to turn on the switch remain with this approach also, and it is possible that an excessive load is applied to the switch, deforming or damaging the switch due to variations in the size of components for pushing the micro switch or torsion of the cover.
Additionally, JP-2009-37997-A proposes an interlock mechanism that includes a pivotable first lever, a second lever pivotably supported on the first lever, and first and second activation portions to selectively rotate the first and the second lever when the cover is closed. The first and second activation portions rotate along the direction in which the cover moves and include cam-shaped contact portions that contact the first and second levers, respectively. However, such complexity makes the mechanism vulnerable to unstable switch operation due to imprecise machining of constituent parts.